Timber element and procedure for manufacturing a timber element

ABSTRACT

The invention concerns a timber element and a procedure for manufacturing such a timber element. The timber element (14b) is composed of at least two heavy wooden blanks (2) fitted one upon the other and glued to each other by their substantially horizontal faces. As taught by the invention, each wooden blank (2) is provided on at least on horizontal face with a guiding recess (6; 6a, 6b) longitudinal to the wooden blank and vertical, for guiding the crackling to occur vertically.

BACKGROUND OF THE INVENTION

The invention concerns a timber element.

The invention also concerns a procedure for manufacturing a timberelement.

Round timbers and dressed timber made from one log are known in priorart. These normal, conventional timbers are frequently subject tocracking as the dry out, in such a way that the splits and cracks becomevisible on the side faces, that is, in the walls of the timber building.The detriment from such cracks is, primarily, aesthetic deficiency: acracked wall surface is no nice view. A further drawback resulting fromthe cracks is impaired insulating capacity of the wall and, further,ready access of water from the exterior surface, through the cracks intothe wood, where damage is likely to ensue.

The state of art knows a timber element which is composed of at leasttwo timber blanks which have been fitted together and glued to eachother. A timber element of this kind, and a procedure for manufacturingsame, is disclosed in the Finnish Patent No. 79966.

In the reference cited, the timber element is made of a wooden blankwhich has been sawn from a log so that the heartwood portion of thetimber lies closer to the horizontal faces of the ultimate timberelement than to its vertical faces exposed to external view. When thisprinciple is followed, cracks will appear in the wooden blank, and alsoin the timber element, mainly on the sawn surfaces lying close to theheartwood, i.e., in the interior of the timber element.

The drawback embarrassing the procedure of the reference is that thecutting of the wooden blank from the log is done with very specialarrangements; the cutting is done, arranging the heartwood portion ofthe wooden blank to lie closer to two given, opposed sides than to theother two opposed sides. The wooden blanks are joined to each other onlyby those sides which lie closer to the heartwood portion, to form atimber element. This procedure aims to benefit of the known fact thatcracks will form in the wood substance on those surfaces which areclosest to the heartwood, when the timber is being dried. However, theprocedure implies careful control and it is therefore highlylabour-intensive. Moreover, the log is not used efficiently when thewooden blank is cut in this manner. All these circumstances contributeto higher manufacturing costs of the timber element.

SUMMARY OF THE INVENTION

The object of the present invention is to disclose a novel timberelement and a novel procedure for manufacturing such a timber element inwhich the drawbacks and problems discussed above can be substantiallyavoided. The object of the invention is, in particular, to provide atimber element which is favourable in manufacturing cost and themanufacturing process of which is, furthermore, simple and reliable.

The timber element of the invention is composed of at least two heavywooden blanks, or deals, fitted one upon the other and joined to eachother by gluing at their substantially horizontal faces. As taught bythe invention, each wooden blank is provided on at least one horizontalface with a guiding recess, longitudinal to the wooden blank andsubstantially vertically directed, to the purpose of guiding thecracking to take place in a vertical direction. The direction of anycracks that may appear in the wooden blank is likely to run towards saidguiding recess because the crack distance is shortest in this particulardirection, and this is therefore the direction in which the deformationstresses produced in the wood when it dries out are most advantageouslydischarged. There may be just one guiding recess longitudinal to thewooden blank, or there may be several recesses side by side.

In an embodiment of the invention, said recess is formed of a pluralityof short recesses disposed with a spacing on one line. It is thusunderstood that the guiding recess may either be one coherent, straightrecess with a length substantially equalling the length of the woodenblank, or a number of consecutive, short recesses in a line.

In an embodiment of the invention, the recess has a wedge-shapedcross-section. Such a wedge-shaped, or conical, recess tapering in theinward direction from the surface of the wooden blank is a naturalstarting point for any crack which may come into being, whereby itsguiding effect is likely to be better than that of any other shape ofrecess, e.g. of a groove with flat bottom.

The procedure of the invention for manufacturing a timber element ischaracterized by that which is stated in claim 4.

In the procedure of the invention for manufacturing a timber elementfrom logs, heavy wooden blanks are cut, these blanks are dried and gluedtogether by their horizontal sides, at least two high, to form timberelement blanks, which are planed prior to being glued together by theirhorizontal faces, and the timber element blank produced by gluing ofthese wooden blanks being machined to ultimate shape, to become a timberelement such as is desired. As taught by the invention, the woodenblanks are provided, subsequent to being cut, on at least one of theiropposed horizontal faces with a guiding recess longitudinal to thewooden blank and substantially vertical, to the purpose of guiding anycracks to run in a vertical direction.

It should be noted that the log cutting takes place in normal manner,considering the predetermined dimensions of the wooden blank, or deal.In all other respects the cutting operation can be managed so as toobtain as its result the optimum quantity of usable sawn timber. Thegreen, sawn wooden blank is then provided with a guiding recess in sucha face which will be located inside in the ultimate timber elementand/or in the top and/or bottom face of the wooden blank. Alternatively,guiding recesses may equally be provided in two opposed, horizontalfaces of such a wooden blank. When, thereafter, the wooden blank isdried, these guiding recesses have the effect that any cracks which formas a result of drying will in all likelihood appear just on the surfaceswhich were provided with guiding recesses and they will therefore belocated in the interior of the timber element that is being produced, oron its top or bottom face. The cracking distance from the centre of thewooden blank to the guiding recess is comparatively minor and thereforethe stresses incurred in drying are likely to find their discharge inthe form of cracks towards the guiding recesses. The guiding recesses onthe wooden blanks will work in like manner in the completed timberelement that has been composed of them. Thus the probability is highthat those sides of the timber element which constitute the wallsurfaces in the completed timber building will remain whole and free ofcracks, which is the object of the invention.

In an embodiment of the procedure of the invention, the guiding recessis shaped to present a conical cross section. The guiding recess mayalternatively be shaped to be a flat-bottomed groove, but a millingcutter or circular saw would have to be used to achieve this. A conicalguiding recess is readily accomplished using e.g. a suitable, wedge-likeblade arrangement; in that case there will for instance be noobjectionable clouds of sawdust. Moreover, such a wedge-shaped recess isin a way a nucleus for splitting and this should facilitate the guidingof any drying cracks specifically towards the guiding recess.

In an embodiment of the procedure of the invention, the guiding recessis incised in a horizontal face of the wooden blank. This can beimplemented by moving the wooden blank on a conveyor past a suitableblade means, said blade means being caused to slash a guiding recess ofappropriate depth longitudinally to the wooden blank in one horizontalface thereof, or in two opposed horizontal faces.

In an embodiment of the procedure of the invention, the guiding recessis provided in a horizontal face of the wooden blank in the form ofshort recesses spaced from each other. It is thus understood that theguiding recess need not be any continuous recess: it can well beimplemented in the form of consecutive recesses disposed in a line, withintact wood substance between them. Such serially arranged recesses aresufficient to guide the splitting, or crack formation, to occurspecifically in that region of the wooden blank where they have beenprovided.

In an embodiment of the procedure of the invention, the guiding recessis embossed in a horizontal face of the wooden blank, using a rotatingblade wheel on which mutually spaced blade elements, such as teeth, havebeen provided. In that case, the wooden blank can be moved on theconveyor past one or two blades so that at least one of the twohorizontal faces becomes embossed with the desired kind of short,serially disposed recesses, which constitute the guiding recess in thiscase. It is also possible, on the other hand, to use the blade wheel astransport means for the wooden blank.

Concerning the advantages afforded by the timber element of theinvention and by its manufacturing procedure, the following additionalobservations can be made.

It is an advantage of the invention that, thanks to the guiding recess,any cracks which may come up during the curing of the wooden blank willbe directed to run to a surface provided with a guiding recess. Theguiding recesses of the wooden blanks elicit the same effect in thecompleted timber element, and therefore the cracking ensuing on thetimber element's drying will take place in the vertical direction of thetimber element, most advantageously in its interior and/or onto the topand/or bottom face of the timber element. Thereby the side faces of thetimber element and the surfaces of any walls that have been erected oftimber elements are kept substantially faultless and, in particular,free of major cracks.

It is a further advantage of the invention that the logs whichconstitute the raw material for the timber element can be cut up intowooden blanks of desired breadth and height, of which the timber elementis composed, in one single work step. It is a further advantage that italso becomes possible to cut the log up more closely not only intowooden blanks for use in making timber elements but also into othertypes of useful timber. It is thus understood that the wooden blanks aresawn to desired dimensions in one go, whereafter they are provided,while still green, with one or two guiding recesses, which arepositioned on predetermined faces, on the whole on flat sides which willbe located inside the timber element and/or on its top and/or bottomface. Subsequent to curing, the wooden blank is planed on the facesmeant to be glued, and the timber element blank assembled ofglued-together wooden blanks is planed/dressed to obtain the desiredsectional configuration, or profile.

It is a further advantage of the invention that the timber elementretains its strength in spite of the guiding recesses used to guide thesplitting, and of any cracks that may form, and that the timber elementkeeps straight and its characteristics remain similar to those of apiece of timber made of a single wooden blank, because the wooden blanksmaking up the timber element are glued together in the horizontal plane.

It is also an advantage of the invention that it is possible by the aidof the procedure to manufacture timber elements of gross dimensions,e.g. 225 mm by 450 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention is described with the aid of attacheddrawings, wherein:

FIG. 1 presents, schematically, a log and the parts into which it iscut;

FIG. 2a presents, schematically, the disposition of a guiding recess onone flat face of the wooden blank and

FIG. 2b, similarly, on two opposed flat faces of the wooden blank;

FIG. 3 illustrates the drying (curing) of wooden blanks;

FIG. 4a shows the planing of one flat of the wooden blank and FIG. 4b,the planing of its opposed flats;

FIG. 5a shows the gluing together of two wooden blanks by their planedflat faces;

FIG. 5b shows the gluing together of three wooden blanks by their planedflat faces;

FIG. 6a presents a timber element blank composed of two wooden blanks;

FIG. 6b presents a timber element blank composed of three wooden blanks;

FIG. 7a presents a completed timber element dressed to prescribedsectional configuration (profile) and which is composed of two woodenblanks;

FIG. 7b presents a timber element composed of three wooden blanks anddressed to prescribed profile;

FIG. 8 shows, schematically, the way in which a conical guiding recessis produced in the wooden blank;

FIG. 9 presents, as seen from one side, the way in which a guidingrecess implemented in the form of short recesses is provided on thewooden blank; and

FIG. 10 presents, as viewed from above, a wooden blank provided with aguiding recess composed of short, consecutive recesses.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1, 2a, 3, 4a, 5a and 6a illustrate a procedure conforming to theinvention serving to manufacture a timber element as shown in FIG. 7a.Similarly, FIGS. 1, 2b, 3, 4b, 5b and 6b illustrate a procedureconforming to the invention serving to manufacture a timber element asshown in FIG. 7b.

In FIG. 1 is depicted a log 1, with the cutting plan perspicuouslytraced on its end face. It is meant to cut the log up into a woodenblank, or batten, 2, of which the breadth l and height k have beenselected in advance. The breadth l of the wooden blank is substantiallyconsistent with the breadth of the timber element to be manufactured,taking into account the curing and machining allowances. The height k ofthe wooden blank is substantially one half or one third of the height ofthe ultimate timber element, accounting for the same allowances. Thus,the breadth l of the wooden blank is as a rule greater than its heightk, in other words, the blank has a rectangular cross section. Inaddition, another batten 3 and a number of boards 4 can be cut from thelog.

When all cutting dimensions, l×k, of the wooden blank have been fixed,it can naturally be cut from any log which is compatible with itsdimensions. All the rest of wood material that will be obtained from thelog 1 can be utilized towards various forms of sawn timber, as battens,boards, etc.

FIG. 2 shows, perspicuously, the disposition of the guiding recess onthe wooden blank 2. In FIG. 2a a guiding recess 6 has been machined inone broad, or flat side 2a of the wooden blank 2a, entering the woodfrom the direction of arrow A with the blade means 5. In FIG. 2b,guiding recesses 6a,6b have similarly been machined with blade means5a,5b in two opposed flat sides 2a,2b of the wooden blank 2, proceedingin the direction of arrows A,B. The flat faces 2a,2b will besubstantially horizontal surfaces in the completed timber element. Theseguiding recesses 6; 6a,6b have been disposed in the longitudinaldirection C of the wooden blank 2 and substantially in the centre of theflat face 2a,2b. The guiding recesses 6; 6a,6b are machined in the greentimber, e.g. in connection with cutting up.

The wooden blanks 2 which have been sawn and provided with one guidingrecess or with several guiding recesses 6a,6b are cured. This may bedone applying any methods and equipment whatsoever intended for timberdrying (curing) known in the art. The wooden blanks may, for instance,be assembled into curing stacks 7 with spacer inserts, the stacks beingtransported on a carriage 8 into the drying chamber 9 for curing in anappropriate artificial atmosphere, as has been perspicuously shown inFIG. 3.

Subsequent to drying, the wooden blanks are taken to be processed formanufacturing timber elements. FIG. 4a illustrates the planing of oneflat side 2a of the wooden blank 2, using a suitable planing apparatus10. Similarly, FIG. 4b illustrates the planing of both flat sides 2a,2bof the wooden blank 2, using planing apparatus 10a,10b. The purpose withplaning is to rectify those surfaces of the wooden blank which will bejoined together in the next work steps. Planing the top and bottom sidesof the timber element to be manufactured is not necessary as a rule.

FIGS. 5a,5b illustrate the assembly of a timber element blank by gluingand pressing of two wooden blanks 2 and of three wooden blanks 2,respectively. A glue course 12 is provided between the surfaces to bejoined of the wooden blanks 2, and the blanks are thereafter pressedtogether in a press means 13 and, if necessary, heated in order toaccelerate the curing of the glue. The wooden blanks 2 may be gluedtogether using any method of prior art whatsoever, such methods beingknown for instance in the manufacturing of glued timber beams.

In FIG. 6a is depicted a timber element blank 11a composed of two woodenblanks 2 and in FIG. 6b, a timber element blank 11b composed of threewooden blanks 2. These timber element blanks are then machined intotimber elements 14a,14b with such profile as may be required, e.g. bybevelling the top edges (15a,15b) in a cutter mill and making a relief16 on the underside, as can be seen for instance in FIG. 7a and 7b,respectively.

The timber element blanks 11a,11b have in this instance been dressedinto timber elements 14a,14b having a profile like that of a dressedtimber. The breadth l of the initial wooden blank 2 is, for instance,225 mm and corresponds also substantially to the breadth l' of thetimber element in FIGS. 6a and 6b. The allowances for machining andcuring are on the order of 1 mm as a rule. Similarly, the height k ofthe wooden blank 2, in the log-cutting situation, is e.g. on the orderof 150 mm, and this also substantially corresponds to the height k' ofthe wooden blank 2 in the dressed timber element 14a,14b in FIGS. 7a and7b. The height of the timber element 14a in FIG. 7a will then be 2×k',or 300 mm, while the timber element of FIG. 6b will have a height of3×k', or 450 mm.

In FIG. 8 is perspicuously shown a means for producing a guiding recess6; 6a,6b in the wooden blank 2. This means enables the guiding recess tobe rapidly and conveniently machined in the wooden blank. The meanscomprises a conical blade component 26, with which the guiding recess 6is incised virtually at right angles into the flat face 2a of the woodenblank 2, to a suitable depth, such as 10 to 30 mm. The taper of theblade component 26 and of the guiding recess 6 has rather beenexaggerated in FIG. 8. The blade component 26 is operated with asuitable actuating means, e.g. with a hydraulic driver 17, by means ofwhich it is urged in the direction A, while the wooden blank 2 istransported on a conveyor 18 past this driver, at a suitable distancefrom it.

FIG. 9 illustrates another means for producing a guiding recess 19 inthe wooden blank 2. This means comprises a blade wheel 20, radiallycarrying blade components, such as teeth 21, spaced at a given distance,and a rotating means, such as an electric motor 22. The distance of thismeans relative to the conveyor 18 is moreover adjustable. When thewooden blank 2 is moved on the conveyor past the blade wheel 20, at asuitable distance therefrom, and the blade wheel 20 is pressed down inthe direction A and set in rotation with the electric motor 22, torotate at a speed which is consistent with the speed at which the woodenblank is being transported, the teeth 21 will sink into the wooden blank2 with a given mutual spacing, and they will in this manner produce aguiding recess 19. This guiding recess 19 has then been incised in thehorizontal face 2a of the wooden blank in the form of short serialrecesses 19a, which are spaced at a given distance. The guiding recess19 has then been established in the shape of a pricked groove, and itoperates in substantially like manner as a continuous guiding recess inthe flat, or horizontal, face of the wooden blank.

The invention is not delimited to read exclusively on the embodimentexample presented: numerous alterations are feasible while stayingwithin the scope of the inventive idea defined by the claims.

I claim:
 1. A timber element, comprising:at least two heavy woodenblanks, each having a substantially horizontal face, said wooden blanksbeing fitted one upon the other and said substantially horizontal facesbeing glued together; a guiding recess being embossed on at least one ofsaid horizontal faces of the corresponding wooden blanks and disposedbetween said glued wooden blanks; and the guiding recess being disposedin a longitudinal direction of the corresponding wooden blank, and adepth of the guiding recess being substantially vertical, for guiding asplitting to occur in a vertical direction, to the corresponding woodenblanks, the guiding recess having a plurality of short recesses disposedin a line with a given spacing.
 2. A timber element according to claim1, wherein the guiding recess presents a wedge-shaped cross section. 3.A method for manufacturing a timber element, comprising the stepsof:cutting at least two heavy wooden blanks from logs, each of the heavywooden blanks providing a horizontal face; embossing a guiding recess inat least one of the horizontal faces in a longitudinal direction of thecorresponding wooden blank, a depth of the guiding recess being in asubstantially vertical direction of the corresponding wooden blank, theguiding recess guiding a splitting to occur vertically, which isvertical to the horizontal faces, the guiding recess including a serialof short recesses spaced at a given distance; planing on the horizontalfaces to be glued; gluing the horizontal faces of at least two woodenblanks, one upon the other, to form a timber element blank; drying thewooden blanks; and shaping the glued wooden blanks to an ultimate shapeby machine, so as to become a desired timber element.
 4. A methodaccording to claim 3, wherein the guiding recess shaped in the shapingstep presents a conical cross section.
 5. A method according to claim 3,wherein the guiding recess shaped in the shaping step is slashed in atleast one of the horizontal faces of the corresponding wooden blank. 6.A method according to claim 3, wherein the guiding recess embossed inthe embossing step uses a blade wheel on which are radially disposedblade components, such as teeth with a given spacing.